The present invention relates to a plug type connection between a thermo feeler and its holder, to be used, for example, for temperature sampling molten steel.
The temperature of molten steel, particularly in the interior of the steel bath, is usually measured by means of a so-called "lost" thermo feeler which in some fashion is fastened to a holder. The fastening should permit that a reliable connection between the components can be made easily and quickly. It is known here to provide the end of the tubular holder with a contact pin and a concentric tubular contact constituting a socket. The thermo feeler has a cylindrical contact carrier made of electrically insulating material and to be plugged into the socket for contact making of and between the respective contacts.
The thermo feeler is usually constructed as thermocouple made from Pt - PtRh wires, having a diameter smaller than 0.2 mm, even smaller than 0.1 mm. These wires or leads have no resiliency and little strength. Thus, they appear not to be suitable directly for contact making, and one has to provide particular contacts for constructing the above-mentioned plug type connection. The contact material, however, cannot be selected in accordance with properties most favorable with regard to contact making and resiliency. Rather, one must consider also the fact that these contacts must be thermoelectrically compatible with the thermocouple leads (see, for example, U.S. Pat. No. 2,823,364). The conductors which run down in the holder, must likewise be compatible with the thermocouple leads. It must be avoided that intermediate contact points and connections become thermoelectrically active in an unforeseen manner. It has, therefore, been suggested to use correspondingly compatible conductors between the thermocouple wires and the contact surfaces proper of the thermo feeler carrier, and all these conductors and contacts are compatible thermoelectrically with the thermocouple (see German printed patent application No. 1,423,936). The problem here is that conductors in the thermo feeler must be electrically connected with the thermo feeler contacts, and the thermocouple leads. The particular configuration of these contacts render the contact making and the establishing of the connection rather cumbersome, including particularly here an insulating support with grooves, etc.